Synthetic biology meets fashion in engineered silk

(Nanowerk News) Scientists have long been fascinated by the extraordinary properties of spider silk, which is stronger than steel yet incredibly light and flexible. Now, Fuzhong Zhang, a professor of energy, environmental and chemical engineering at the McKelvey School of Engineering at Washington University in St. Louis, has made significant breakthroughs in the manufacture of synthetic spider silk, paving the way for a new era of sustainability. clothing production.

Since engineering recombinant spider silk in 2018 using bacteria, Zhang has worked to increase the yield of microbial-generated silk threads while retaining the desired properties of increased strength and toughness.

Higher yields will be critical if synthetic silk is to be used in everyday applications, especially in the fashion industry where renewable materials are urgently needed to stem the environmental impact that comes from producing around 100 billion garments and 92 million tons of waste each year. .

With the help of engineered mussel foot proteins, Zhang has created a new spider silk fusion protein, called bi-terminal Mfp fused silks (btMSilks). Microbial production of btMSilks has an eightfold higher yield than recombinant silk protein, and btMSilk fibers substantially increase strength and toughness while being lightweight. This could revolutionize clothing manufacturing by providing a more environmentally friendly alternative to traditional textiles.

The findings were published in Nature Communications (“The bi-terminal fusion of the intrinsically disorganized clam leg protein fragments enhances the mechanical strength for the protein fiber”).

“The outstanding mechanical properties of natural spider silk stem from its very large and repeating protein sequences,” said Zhang. “However, it is very challenging to ask fast-growing bacteria to produce lots of repeat proteins.

“To solve this problem, we need a different strategy,” he said. “We were looking for a disordered protein that could be genetically fused with silk fragments to drive molecular interactions, so that strong fibers could be made without using large repeating proteins. And we actually found that here in the work that we’ve done on clam leg proteins.

Scallops secrete this special protein in their feet to attach to things. Zhang and his collaborators have engineered bacteria to produce it and engineered it as an adhesive for biomedical applications. As it turns out, the leg proteins of clams are also cohesive, which allows them to stick to one another so well. By placing clam leg protein fragments at the ends of his synthetic silk protein sequences, Zhang created a less repetitive and lightweight material that is at least twice as strong as recombinant spider silk.

Yields on Zhang’s material increased eightfold compared to previous studies, reaching 8 grams of fiber material from 1 liter of bacterial culture. This output constitutes sufficient fabric to be tested for use in a real product.

“The beauty of synthetic biology is that we have a lot of room to explore,” said Zhang. “We can cut and paste the sequences of various natural proteins and test these designs in the laboratory for new properties and functions. This makes synthetic biological materials much more flexible than traditional petroleum-based materials.”

In future work, Zhang and his team will expand the tunable properties of their synthetic silk fibers to meet the precise needs of each specialty market.

“Because our synthetic silk is made from inexpensive raw materials using engineered bacteria, it presents a renewable and biodegradable substitute for petroleum-derived fiber materials such as nylon and polyester,” said Zhang.